This multiple unit control board is an accessory used when
you need to control up to 3-units from a single thermostat .
The board is typically mounted in the unit control box clos-
est to the thermostat . A maximum of 2 boards may be used
together if up to 6-units must be connected and controlled
from a single thermostat .
This version of the board uses VAC relays and should not
be used in combination with any other accessories or equip-
ment that require VDC connections to the “G”, “W1”, or “Y1”
terminals (i .e . Boilerless System Kit) .
The multiple unit control board provides the components
necessary to protect the Mark IV/AC board from electrical
damage that may occur when using standard off-the-shelf
relays .
Do not use the unoccupied (U-terminal) feature with the
multiple unit control board .
Multiple Unit Control (up to 3 units) (P/N 056794201)
Page 18 / IM 742
WSHP Mark IV/AC Board Low Voltage Terminal Strip
O W2 G W1 Y1 F E L U A P V R C
1
2
3
Auxiliary Relay
Orange
Yellow
White
WSHP Mark IV/AC Board Low Voltage Terminal Strip
O W2 G W1 Y1 F E L U A P V R C
1
2
3
Auxiliary Relay
Orange
Yellow
White
Options on Mark IV/AC Units
The auxiliary relay is designed to interface external equip-
ment with the Mark IV/AC board . The auxiliary relay
has been provided with the components necessary
to protect from electrical damage that may occur to the
Mark IV/AC board when using standard off-the-self relays .
The auxiliary relay can be used to provide fault signals,
unit operation signals, or to provide a means for remote
equipment to control the Mark IV/AC board . The orange,
yellow, and white connections are short flying leads
pre-attached to the board . The diagrams shown are some
connection examples .
Auxiliary Relay (P/N 106059701)
WSHP Mark IV/AC Board Low Voltage Terminal Strip
O W2 G W1 Y1 F E L U A P V R C
1
2
3
Auxiliary Relay
Orange
Ye
llo
w
White
Operation:
In this example the
auxiliary relay contacts can be
used to indicate a fault condi-
tion . With the auxiliary relay
connected as shown, the nor-
mally open contacts will close
during a fault condition .
Operation:
In this example the
auxiliary relay contacts can be
used to signal WSHP fan oper-
ation to another device . In this
example when the thermostat
energizes the “G” terminal the
auxiliary relay normallyopen
contacts wil close .
Operation: In this example the
auxiliary relay is used to interface
other control devices to the Mark
IV/AC board . Using the Orange
(-) and White (+) wires, and 24vac
or 24vdc, another device could be
used to start and stop the WSHP
heating sequence .
O W2 G W1 Y1 F
E L
U A P V
R C
WSHP Mark IV/AC Board Low Voltage Terminal Strip
O W2 G W1 Y1 F
E L
U A P V
R C
O W2 G W1 Y1 F
E L
U A P V
R C
R
Y
G
W
R
Y
G
W
R
Y
G
W
G W Y R
C
G W
1 Y
1 R Rc C
Thermostat Terminals
Multiple Unit
Control Panel
TB3
TB2
TB1
TB4
WSHP Mark IV/AC Board Low Voltage Terminal Strip
WSHP Mark IV/AC Board Low Voltage Terminal Strip